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| Started by | Waiman Long <Waiman.Long@hpe.com> |
|---|---|
| First post | 2015-09-11 20:40 +0200 |
| Last post | 2015-09-18 11:00 +0200 |
| Articles | 2 — 2 participants |
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[PATCH v6 2/6] locking/pvqspinlock: Unconditional PV kick with _Q_SLOW_VAL Waiman Long <Waiman.Long@hpe.com> - 2015-09-11 20:40 +0200
[tip:locking/core] locking/pvqspinlock: Kick the PV CPU unconditionally when _Q_SLOW_VAL tip-bot for Waiman Long <tipbot@zytor.com> - 2015-09-18 11:00 +0200
| From | Waiman Long <Waiman.Long@hpe.com> |
|---|---|
| Date | 2015-09-11 20:40 +0200 |
| Subject | [PATCH v6 2/6] locking/pvqspinlock: Unconditional PV kick with _Q_SLOW_VAL |
| Message-ID | <q7BoS-1rn-3@gated-at.bofh.it> |
If _Q_SLOW_VAL has been set, the vCPU state must have been vcpu_hashed.
The extra check at the end of __pv_queued_spin_unlock() is unnecessary
and so is removed.
Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
---
kernel/locking/qspinlock_paravirt.h | 6 +-----
1 files changed, 1 insertions(+), 5 deletions(-)
diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index c8e6e9a..f0450ff 100644
--- a/kernel/locking/qspinlock_paravirt.h
+++ b/kernel/locking/qspinlock_paravirt.h
@@ -267,7 +267,6 @@ static void pv_wait_head(struct qspinlock *lock, struct mcs_spinlock *node)
}
if (!lp) { /* ONCE */
- WRITE_ONCE(pn->state, vcpu_hashed);
lp = pv_hash(lock, pn);
/*
@@ -275,11 +274,9 @@ static void pv_wait_head(struct qspinlock *lock, struct mcs_spinlock *node)
* when we observe _Q_SLOW_VAL in __pv_queued_spin_unlock()
* we'll be sure to be able to observe our hash entry.
*
- * [S] pn->state
* [S] <hash> [Rmw] l->locked == _Q_SLOW_VAL
* MB RMB
* [RmW] l->locked = _Q_SLOW_VAL [L] <unhash>
- * [L] pn->state
*
* Matches the smp_rmb() in __pv_queued_spin_unlock().
*/
@@ -364,8 +361,7 @@ __visible void __pv_queued_spin_unlock(struct qspinlock *lock)
* vCPU is harmless other than the additional latency in completing
* the unlock.
*/
- if (READ_ONCE(node->state) == vcpu_hashed)
- pv_kick(node->cpu);
+ pv_kick(node->cpu);
}
/*
* Include the architecture specific callee-save thunk of the
--
1.7.1
--
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| From | tip-bot for Waiman Long <tipbot@zytor.com> |
|---|---|
| Date | 2015-09-18 11:00 +0200 |
| Subject | [tip:locking/core] locking/pvqspinlock: Kick the PV CPU unconditionally when _Q_SLOW_VAL |
| Message-ID | <q9ZGs-67w-55@gated-at.bofh.it> |
| In reply to | #1223029 |
Commit-ID: 93edc8bd7750ff3cae088bfca453ea73dc9004a4
Gitweb: http://git.kernel.org/tip/93edc8bd7750ff3cae088bfca453ea73dc9004a4
Author: Waiman Long <Waiman.Long@hpe.com>
AuthorDate: Fri, 11 Sep 2015 14:37:34 -0400
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 18 Sep 2015 09:27:29 +0200
locking/pvqspinlock: Kick the PV CPU unconditionally when _Q_SLOW_VAL
If _Q_SLOW_VAL has been set, the vCPU state must have been vcpu_hashed.
The extra check at the end of __pv_queued_spin_unlock() is unnecessary
and can be removed.
Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1441996658-62854-3-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/locking/qspinlock_paravirt.h | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index c8e6e9a..f0450ff 100644
--- a/kernel/locking/qspinlock_paravirt.h
+++ b/kernel/locking/qspinlock_paravirt.h
@@ -267,7 +267,6 @@ static void pv_wait_head(struct qspinlock *lock, struct mcs_spinlock *node)
}
if (!lp) { /* ONCE */
- WRITE_ONCE(pn->state, vcpu_hashed);
lp = pv_hash(lock, pn);
/*
@@ -275,11 +274,9 @@ static void pv_wait_head(struct qspinlock *lock, struct mcs_spinlock *node)
* when we observe _Q_SLOW_VAL in __pv_queued_spin_unlock()
* we'll be sure to be able to observe our hash entry.
*
- * [S] pn->state
* [S] <hash> [Rmw] l->locked == _Q_SLOW_VAL
* MB RMB
* [RmW] l->locked = _Q_SLOW_VAL [L] <unhash>
- * [L] pn->state
*
* Matches the smp_rmb() in __pv_queued_spin_unlock().
*/
@@ -364,8 +361,7 @@ __visible void __pv_queued_spin_unlock(struct qspinlock *lock)
* vCPU is harmless other than the additional latency in completing
* the unlock.
*/
- if (READ_ONCE(node->state) == vcpu_hashed)
- pv_kick(node->cpu);
+ pv_kick(node->cpu);
}
/*
* Include the architecture specific callee-save thunk of the
--
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the body of a message to majordomo@vger.kernel.org
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